Gigantic Gravity "Lenses" Magnify Galaxies Far, Far Away

This diagram illustrates a cosmic phenomenon known as gravitational lensing, in which a nearby galaxy distorts, but also magnifies a second, more distant galaxy in the background, making it appear brighter and easier to study. In the diagram, Earth is shown to the left. A foreground galaxy is shown in blue. A more distant galaxy is shown in red. The gravity of the foreground galaxy bends the light from the distant one, as shown with the lines.

The lensing effect leads to a distorted and magnified view of the distant galaxy. An example of a final image taken by ground-based telescopes is at the right, where in blue is the visible light from the foreground galaxy and in pink is the sub-millimeter wavelength emission from the background galaxy. As illustrated on the bottom, the lensing effect due to gravity can be compared to bending of light when passing through a medium of varying index of refraction, such as a glass containing water. The light bending through water results in a distorted view of the background object.

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This image composite shows a warped and magnified galaxy discovered by the Herschel Space Observatory, one of five such galaxies uncovered by the infrared telescope. The galaxy, named SDP 81 is the yellow dot on left and the pink smudges on right. It is so far away that its light took about 11 billion years to reach us. Herschel was able to find the galaxy, which is buried in dust, because it happens to be positioned behind another galaxy (blue blob at right) that is magnifying it. The foreground galaxy's gravity is distorting and magnifying the distant galaxy's light, causing it to appear in multiple places, as seen as the pink smudges.

Herschel couldn't detect the foreground galaxy, but astronomers were able to spot it in optical light using the W.M. Keck Observatory. Several follow-up observations by ground telescopes also helped to get a better view of the distant galaxy. For example, the pink smudges at the right show wavelengths that are even longer than what Herschel sees in the submillimeter portion of the electromagnetic spectrum. The observations were taken by the Smithsonian Astrophysical Observatory's Submillimeter Array in Hawaii.